To Edit a Custom Tolerance Method (AutoCAD Mechanical Toolset)

You can change an existing tolerance method by editing the corresponding tolerance expression in system settings.

1. At the Command prompt, enter AMOPTIONS.
2. In the Options dialog box, select the AM:Preferences tab and click System. The System Editor opens.
3. In the navigation area (the left side of the dialog box), expand Acad/M DimSet Tols.
4. Click the entry corresponding to the tolerance method you want to change.
   
5. In the variable area (top-right side of dialog box), double-click the key TolStr. The Value dialog box is displayed.
Note: Depending on the fit representation you selected, you may need to edit a few other tolerance expression keys besides TolStr. Click the Related Concepts link and expand the section The keys under the entries “Fits" and “Tols" for details on the keys.
6. In the Value box, enter a valid tolerance expression (a combination of MTEXT format codes and special characters). For example, $T {H0.7x;$2 A0;S$+$P^$-$M;}.
   Note:

   • To see a list of MTEXT format codes commonly used in tolerance expressions, click the Related Concepts link and expand the section MTEXT format codes used in Tolerance Expressions.
   • To see a list of special characters commonly used in tolerance expressions, click the Related Concepts link and expand the section Special Characters used in Tolerance Expressions.
   • To see examples, click the Related Concepts link and expand the section Examples.
7. Click OK.
8. In the navigation area, click the entry corresponding to the alternate units (the tolerance method that has the same name as the one you chose in step 4, followed by the word "-alt").
9. Repeat steps 5 through 7.